In a multimedia data transmission system, two or more users or groups at different places send multimedia data such as sound, video and documents to each other through transmission lines and multimedia devices, so as to achieve immediate and interactive communication, and thus a conference may be implemented.
FIG. 1 is a schematic diagram illustrating a conventional multimedia data transmission system. As shown in FIG. 1, the system includes a Multi-point Control Unit (MCU) and clients. The MCU communicates with the clients by using a private network. The MCU includes a multi-point controller and a multi-point media processor. The multi-point controller may be a multimedia conference server. The multimedia conference server may provide users with a plurality of virtual multimedia conference rooms. A user may select or create a multimedia conference room via the client. After accessing to the multimedia conference room, the user may interact with other users accessing to this multimedia conference room with multimedia data.
The multimedia data transmission system mainly involves singling transmission, singling control among server systems and multimedia data transmission. The signaling transmission is used in interaction between the multi-point controller and the clients. The signaling control among server systems is used in interaction between the multi-point controller and the multi-point media processor. The multimedia data transmission is used in interaction between the multi-point media processor and the clients. When a user wants to access to the multimedia data transmission system, the user interacts with the multi-point controller via the client through signaling interaction between the client and the multi-point controller, the multi-point controller interacts with the multi-point media processor through signaling control between the multi-point controller and the multi-point media processor, and the user is accessed to the multimedia conference room of the multimedia data transmission system according to a result of interaction between the multi-point controller and the multi-point media processor, and thus sharing of multimedia data may be performed.
FIG. 2 is a schematic flowchart illustrating a conventional method for transmitting multimedia data based on FIG. 1. As shown in FIG. 2, the method includes processing as follows.
At 201, a client sends a multi-point controller a multimedia call signaling and establishes a call connection.
The client may access to a multimedia data transmission system in a login mode or in a registration mode. If the login mode is selected, the multimedia call signaling includes information such as a user number, a user password and identification of a multimedia conference room and the like. If the registration mode is selected, the multimedia call signaling may not include any information.
The multimedia conference room may be an audio conference room, a video conference room or a data conference room.
By using the multimedia call signaling, the client and the multi-point controller may perform processing, such as call establishment, call processing, call warning, call connection and call release.
At 202, the multi-point controller and a multi-point media processor establish an accessing channel between the client and the multimedia conference room through signaling control among server systems.
If the login mode is selected, the multi-point controller performs authentication for a user. After the user passes the authentication, the multi-point controller interacts with the multi-point media processor through the signaling control among the server systems, allocates transmission bandwidth to the user, configures an input channel and an output channel, obtains a multimedia conference room corresponding to the identification of the multimedia conference room from the multi-point media processor, and establishes an accessing channel between the user and the multimedia conference room. If the registration mode is selected, the multi-point controller obtains multimedia conference rooms from the multi-point media processor, displays the obtained multimedia conference rooms to the client, so that the user may select a desired multimedia conference room or create a new multimedia conference room and perform registration. After the user's registration succeeds, the multi-point controller allocates transmission bandwidth to the user, configures an input channel and an output channel, and establishes an accessing channel between the user and the multimedia conference room. When a new multimedia conference room is created, the multi-point controller creates a mixer, for example, a multi-picture mixer, a sound mixer, for the user, and adds the input channel and the output channel.
At 203, the multi-point controller returns a multimedia call signaling response to the client.
At 204, the client accesses to the multimedia conference room, encodes multimedia data, and sends the encoded multimedia data to the multi-point media processor.
After determining to share the multimedia data, such as video data, with other members of the multimedia conference room, the user obtains video image information via the client, performs processing such as encoding and compressing for the video image information, and transmits the processed video image information to the multi-point media processor.
Real-time Transport Protocol (RTP) and Real-time Control Protocol (RTCP) may be used in transmission of the multimedia data between the multi-point media processor and the client.
At 205, the multi-point media processor receives the multimedia data sent by each client, decodes the multimedia data, and composes each decoded multimedia data.
In a multimedia conference room, for example, a video conference room, each member needs to know the video information of other members in real time, the multi-point media processor decodes the multimedia data sent by each client, and composes each decoded multimedia data to include the multimedia data of each client in the composed multimedia data.
At 206, the multi-point media processor encodes the composed multimedia data, and then sends it to each client for displaying.
The multi-point media processor encodes the composed multimedia data, and then sends the encoded multimedia data to each client in the multimedia conference room by means of broadcasting. The client receives the encoded multimedia data, decompresses and decodes the received encoded multimedia data, and displays the multimedia data. Thus, the user may obtain the multimedia data of other users in real time, and thus the multimedia data is shared among users.
Further, the multi-point media processor may reduce network packet loss by using a strategy of retransmitting lost packets, so as to ensure the reliability of the multimedia data transmission.
As can be seen, in the conventional multimedia data transmission system, the multi-point media processor is required to perform the processing of decompressing, decoding, compressing, encoding and the like for the received multimedia data such as audio and video data stream. Since a large number of clients are accessed to the multi-point media processor, there is a high requirement for the data processing performance of the multi-point media processor. Since high cost is needed to improve the data processing performance of the multi-point media processor, the use cost of the multimedia data transmission system is increased.